Machinable and hardenable alloys of hard material are known in many variations. Because these hard material alloys have an alloy content of nearly 50 volume percent carbide, preferably titanium carbide, thermal expansion of these alloys is less than tool steel. Since these hard material alloys are often undetachably joined to tool steel by a sintered bond, the differences in thermal expansion of the tool steel and the hard materials create stresses between the alloys which can generate cracks under a slight temperature rise.
If the hard material alloy is joined to tool steel by a detachable joint, such as by fitting, bolting, cementing or the like, the differences in thermal expansion of the hard material alloy and the tool steel will create air gaps between the two alloys when the tool steel and/or the hard material alloy are heated up. These air gaps create a situs for pieces of the material be be machined, e.g., plastic, to settle to become a hard to remove burr between the machine parts.
In order to eliminate this problem, attempts were made in the past to formulate hard material alloys having a coefficient of thermal expansion as close as possible to that of the tool steel to which it will be joined.
Hard material alloys having the composition disclosed herein, minus the aluminum content, are known in the art. Examples of these alloys are seen in German Patents Nos. 2,000,257; 2,008,197 and 2,059,251.
Accordingly, it is an object of the invention to formulate a hard material alloy which can be joined to a tool steel member by a sintered bond wherein no cracks will be created as the tool is heated up.
It is a further object of the invention to formulate a hard material alloy which can be detachably joined to a tool steel member wherein there will be no air gaps created at the alloy interface upon heating.
It is a further object of the invention to create a hard material alloy having a coefficient of thermal expansion approximately equal to the tool steel to which it is joined.